Finite Element Modeling Of The Interaction Between Vessel And Microbubble Activated By Ultrasound

Well understanding the oscillation behavior of coated-microbubble restrained within an elastic microvessel is significant for safe applications of ultrasound contrast agents (UCAs) in imaging and clinical therapy. A two-dimensional (2D) asymmetric finite element model was developed to simulate the two-way-coupled interactions in the bubble-blood-vessel system. In the numerical simulations, the influences of both acoustic driving parameters and material properties on the dynamic interactions in the system were investigated. As the result shown, the radial directional restrained effect induced by the vessel wall will result in the vessel deformation, asymmetric bubble oscillation, and the increase of bubble resonance frequency. For a case in which a bubble (1.5-μm initial radius) activated by an ultrasound pulses (1-MHz frequency) oscillated in a microvessel with a radius varying in a range of 2-6.5 μm, the shear stress generated by bubble oscillation on the vessel wall could reach to 26.95 kPa (high enough to induce damage of vascular endothelial cells) when the driving pressure reached to 0.2MPa.With the acoustic driving pressure or the blood viscosity increasing, or with the vessel size and the microbubble shell visco-elastic properties decreasing, the bubble’s asymmetrical oscillation ratio could be aggravated from 0.12% to 79.94%. By the increasing vessel size and acoustic pressure, or the decreasing microbubble shell visco-elasticity and blood viscosity, the maximum compression velocity on the bubble will be enhanced from 0.19 m/s to 22.79 m/s. As the results, the peak values of shear stress induced by microstreaming on the vessel wall increases from 0.003 to 26.95 kPa and the deformation degree of vessel is increased from 1.01 to 1.49, due to the enhanced acoustic amplitude, or the decreasing vessel size, blood viscosity and microbubble shell visco-elasticity. In addition, it also suggests that, among above impact parameters, microbubble resonance frequency and UCA shell elasticity might play more dominant roles in dynamic interactions of the bubble-blood-vessel system.